(CNN) -- Thousands of Argentine protesters opposed to a same-sex marriage bill to be debated in the Senate demonstrated in front of Argentina's Congress Tuesday.

The Argentine Senate is to vote Wednesday on a gay marriage bill that has already passed the lower chamber of Congress. The bill would give same-sex couples equal marriage rights, including the ability to adopt children.

Tuesday's marches were convened by the Catholic and evangelical churches in Argentina, under the banner, "Children have a right to a father and a mother," the state-run Telam news agency reported.

"We are not against any community, but we want to be clear: marriage is between a man and a woman and the rights of children to have a father and mother cannot be violated," one of the organizers told reporters.

The large crowd waved Argentine flags and held banners and balloons. There was also live music.

"We don't want a negative tint, that's not the objective of the march, but to propose and promote marriage as we understand it, between a man and a woman, and express rejection to the bill passed by the (lower house of) Congress," Justo Carbajales, representative of the Episcopal Church in Argentina, told Telam.

A smaller, but just as boisterous, group of counter-protesters in favor of the same-sex marriage bill congregated in another part of the city.

Last month's congressional vote and Wednesday's Senate vote are the latest moves in a pro-gay marriage trend in Argentine politics.

Last year, a judge in the capital of Argentina, Buenos Aires, ruled that a ban on same-sex marriage was illegal, paving the way for gay marriages in the capital. An injunction filed by another judge stopped what would have been the first gay marriage there. Ultimately, Latin America's first gay marriage happened in Argentina in a southern state with a pro-gay marriage governor.

Now, the issue has reached beyond local and state politics to the national stage.